Defining Feasibility and Pilot Studies in Preparation for Randomised Controlled Trials: Development of a Conceptual Framework

Sandra M. Eldridge, Gillian A. Lancaster, Michael J. Campbell, Lehana Thabane, Sally Hopewell, Claire L. Coleman, Christine M. Bond

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We describe a framework for defining pilot and feasibility studies focusing on studies conducted in preparation for a randomised controlled trial. To develop the framework, we undertook a Delphi survey; ran an open meeting at a trial methodology conference; conducted a review of definitions outside the health research context; consulted experts at an international consensus meeting; and reviewed 27 empirical pilot or feasibility studies. We initially adopted mutually exclusive definitions of pilot and feasibility studies. However, some Delphi survey respondents and the majority of open meeting attendees disagreed with the idea of mutually exclusive definitions. Their viewpoint was supported by definitions outside the health research context, the use of the terms ‘pilot’ and ‘feasibility’ in the literature, and participants at the international consensus meeting. In our framework, pilot studies are a subset of feasibility studies, rather than the two being mutually exclusive. A feasibility study asks whether something can be done, should we proceed with it, and if so, how. A pilot study asks the same questions but also has a specific design feature: in a pilot study a future study, or part of a future study, is conducted on a smaller scale. We suggest that to facilitate their identification, these studies should be clearly identified using the terms ‘feasibility’ or ‘pilot’ as appropriate. This should include feasibility studies that are largely qualitative; we found these difficult to identify in electronic searches because researchers rarely used the term ‘feasibility’ in the title or abstract of such studies. Investigators should also report appropriate objectives and methods related to feasibility; and give clear confirmation that their study is in preparation for a future randomised controlled trial designed to assess the effect of an intervention.
Original languageEnglish
Article numbere0150205
Pages (from-to)1-22
Number of pages22
JournalPloS ONE
Issue number3
Publication statusPublished - 15 Mar 2016

Bibliographical note

We thank Alicia O’Cathain and Pat Hoddinot for discussions about the reporting of qualitative studies, and consensus participants for their views on our developing framework. Claire Coleman was funded by a National Institute for Health Research (NIHR) Research Methods Fellowship. This article presents independent research funded by the NIHR. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.

Funding: The authors received small grants from Queen Mary University of London (£7495), University of Sheffield (£8000), NIHR RDS London (£2000), NIHR RDS South East (£2400), Chief Scientist Office Scotland (£1000). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.


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